Today, I designed a parametric model of a structural overhead tank with the functionality to increase the number of storeys. All the components (columns, beams, ring beam, bottom dome, tank wall and top dome) of this tank depend on only 2 parameters. They are the radius of the column and the number of columns in the z-direction.
After opening the file, expand the ‘ZColumnArray’ and select the ‘ColumnSketch’ in the tree view. In its data properties, you can change the radius of the column in the constraints section. Select ‘ZColumnArray’ and go to ‘Number Z’ in the data properties. Here you can change the number of columns in Z-direction.
Certain expressions are used to set the dependent constraints. Refer this link for further readings: (https://www.freecadweb.org/wiki/Expressions)
The FreeCAD file of this model can be downloaded from this link: ParametricTank
Feel free to test and review this parametric model.